Light signal



Patented Jane 24, 193% UNTEIE d'TAES PATNT CHARLES W. PRESCOTT, CF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILVJAY SIGEIAL OIEIEANY, OF ROCHESTER, NEW YORK LIGHT SIGNAL Application filed July 11, 1924. Serial No. 725,389.

This invention relates to light signals, and more particularly to means for positively and unmistakably detecting at some distant point whether the illuminted signal is actually displayed.

In the provision of signals for railway signalling purposes and the like, whether such signals are of the color light, position light or semaphore type it is extremely import-ant to be able to indicate reliably at a pointcistant from such signal whether or not such signal is illuminated. The stop signal indication is important so as to insure that all si nals authorizing conflicting movements are at stop before a signal in question is moved to the proceed position {6) that all signals authorizing movements over a switch or derail are at stop before the position of the switch or derail can be altered, and (0) that one signal in an automatic block si nal system is actually indicating stop berore the signal in the rear is allowed to indicate proceed, also, in certain cases it is desirable to substitute another illuminated signal for a certain signal when the filament of the latter signal burns out.

It has heretofore been recognized that the display of a light signal may be fairly reliably indicated by detecting the flow of our- 3 rent in a circuit leading to the filament of a si nal lamp, this method of indication is, however, not absolutely reliable because the filament of the lamp may be partially shunted and it such filament burns out enough cur rent might possibly still flow through such shunt to give a false indication by indicating illumination of such signal when it is in fact not illuminated.

Will the above and other considerations in mind, the principal objects and purposes of the present invention contemplate the provision of means responsive to the illumination of the filament or a lamp, that is, the electronic emission from the filament, rather than the presence or current flowing in a circuit leading to such lamp, by determining whether or not the space immediately surrounding the filament of the lamp is ionized. More specifically, it is proposed to provide an additional element or elements within the lamp suitably spaced from the filament therein so that the lamp constitutes a two or three element vacuum tube, which if a two element device is commercially known as the Fleming valve, and it a three element device is known as a De Forest amplifier, to provide a circuit leading from this additional element or plate back to the filament which includes a source of energy and a relay or other suitable type of electro responsive device, whereby current will only flow in this latter circuit so long as the space between the filament and plate is ionized.

Another object of the present invention more particularly attainable when signal lamps are energized by alternating current, consists in the means of supplying unidirectional current of definite polarity in the event the filament of a certain lamp energizable by alternating current is in fact illuminated. This current is distinctive from the operating and control current and in connection with suitable selecting apparatus responsive to uni-directional current of one polarity only, may be used to make impossible a false or erroneous indication by reason of accidental crosses between wires.

Other objects, purposes and characteristic features or" the present invention consists in employing this method of determining when the filament of a certain lamp is illuminated in various kinds of circuit arrangements, in some of which the same wires are used for signalling and indicating purposes and in others of which the extinguishing of one lamp illuminates a substitute lamp.

Other objects, purposes and characteristic features of the invention will appear as the description thereof progresses.

In describing the invention in detail reference will be made to the accompanying drawing in which Fig. 1 illustrates in a simple and diagrammatic manner how an indication relay may be energized in response to the illumination of a signal lamp of the two element type;

Fig. 2 illustrates a circuit arrangement similar to Fig. l in which the indication relay only responds if the filaments of two lamps are both illuminated;

Fig. 3 shows a circuit arrangement in which an alternating current relay may be controlled from a distant point overapair of wires one of which may be used to indicate by the thermionic principle whether a lamp controlled by such relay is energized;

Fig. 1 illustrates a three-position light signal two lamps of which comprise Flem ing valves and in which the third lamp is: illuminated whenever neither of the other lamps are illuminated;

Fig. 5 is a sectional. side elevation of a light signal embodying applicants invention and including a lamp having a plate therein which serves as a shield against phantom and also as an element to detect illumination of the filament; and

Fig. 6 is a front elevation of the filament of sald lamp.

Referring to Fig. 1 there has been shown conventionally a lamp having a concentrated filament F therein specially designed for emitting light from a point sour *e, and in which a secondary element or plate I is rovided properly spaced and insulated rom the filament F. This lamp has been shown supported on a signal pole 1 and is intended to represent the light source of a suitable railway signal. In practice this lamp or Fleming valve 7 is specially designed so as to serve both as a concentrated source of light for signalling purposes and as a means for controlling the flow of and rectifying alternating current for detecting whether such light source is present. Any of the well known expedients such as coated filaments, impregnated filaments, and extremely highly evacuated bulbs may be used to make the device suitable for the purposes intended.

In Fig. 1 has been shown an indication relay IR connected in a circuit including the plate P so that this relay may respond to a flow of a predetermined amount of current toward the plate P. This relay IR may be of any desired construction, may be one of the type responsive to either alternating current or direct current, but is preferably responsive to direct current flowing in one direction 0111'. This indication relay IR may be user to control indicators, pilot lamps, electrically operated dogs and indication magnets. if desired. The particular circuit arrangement shown in Fig. 1 is merely illustrative of how an indication rclay may be operated responsive to, and only responsive to, the illumination of a particular light or semaphore signal lamp, as determined by the presence of ionized gas immediately surrounding the filament of such lamp.

In Fig. 1 the filament F is connected directly across the secondary winding of a transformer 2, which in turn has its primary winding connected to one secondary winding 5 of a transformer 3 through a suitable controllable contact 4, this transformer 3 having its primary winding connected to a suitable source of alternating current AC. The contact 4 may either be manually operated or may comprise either a front or a back contact of a suitable relay as the circumstances of the case may require. \Vith the switch or contact 4 closed the filament F is energized thereby displaying a signal of a certain color or character providing the circuits through which energy is carried to the filament F are not interrupted or open at any point. \Vith the filament F energized to an extent to properly illuminate the signal in question the space between the filament F and the plate P is ionized to rather freely permit the flow of current from the plate P to the filament F, at least if a source of potential is applied thereto. In the particular arrangement shown the secondary winding 6 of the transformer 3 has been provided for affording such source of potent tial. This windim 6 has its one end connected to the middIe point of the secondary winding of the transformer 2 and its other end connected to the plate P through the indication relay IR. From this it will read ily appear that if the various parts are properly designed and proportioned that the relay IR will assume its energized position as soon as the f lament F is energized to a predetermined extent, and that if the filament F burns out, or the source of energy partially fails or is cut off entirely for some other reason, the relay IR- assumes its deenergized position.

In Fig. 2 have been illustrated two lamps 11 and 12 similar to the lamp 7 shown in Fig. 1. In this arrangement it is intended to give an indication, by causing energization of the relay IR only if both the lamps 11 and 12 are properly illuminated. One example or instance in which it may be desirable to indicate whether all of a group of lamps are energized, consists in a series of red lamps to stop traffic over a plurality of routes conflicting with a certain route over which a train is passing or is permitted to pass by reason of a proceed signal, and in this case the interlocking mechanism is preferably so constructed that no clear or proceed signal can be given over the route in question until the stop or red signals for all of the conflicting routes are actually illuminated.

In Fig. 2 the lamp 11 has its filament connected across the secondary winding of a transformer 13 and this lamp may be controlled by levers, track relays and the like, so as to energize the primary winding of this transformer 13 when the lamp 11 should be illuminated, the lamp 12 being connected in asimilar manner to a transformer 14. The indication relay IR in this instance has one of its lead wires connected in series with the secondary winding of the transformer and has the gaps contained between filaments F and plate of the lamps 11 and 12 connected in series there; ith. if both the lamps 11 and 12 are illun i rated sufiicient current will flow in the indication relay IR to cause it to assume its energizedposition through the tolloning circuit :-beginning at the secondary winding of the transformer 15, wire 16, plate P to filament F of the lamp 12, from the middle point of the secondary winding of the transformer A through wire 17 to the plate P or lamp 11, through the ionized or gap of lamp 11 to filament F thereof, to the secondary winding of the transformer 13, and from too mic dle point mg to the wire 18, through the winding of the relay IR- hack to the secondary winding of the transformer 15. @hvicusly, if either the lamp 11 or the lamp 12 is extinguished the circuit just traced is practically open, so that the relay sumes its tie-energized position.

In Fig. 3 has been shown an arrangement similar to that of Fig. 1 in which a relay DC responsive only to the flow or" direct current is used, and in which certain oi the wires are used for both indicating and signalling purposes. In this arrangement the lamp 20 has its filament F connected across the secondary winding of the transforms" 21, which in its normal condition shown is ene 'iZed by the secondary windin. 22 of a l i i transformer 23 through a circuit which may 13 traced follows :hee inning at the secondary winding 22, wires 2- and primary ring of the transformer 21, wire 2?, bacl:

act 27 of the al=;-ernatingcurrent rcla 28 and 29, back e3 the ndaiy lamp 20 is illumiwinding so that nate-l when the alternati current r lav it is in its (lo-energized 0sion lVith the lamp 20 lllulllillmled sufficrent current 101 DC n its energized p 3 tie is caused to flow in the following circuit:-beginning the secondary winding 22 of the transformer 23, wires 24;, and 30, filament F of the lamp 20, through the ionized gas to the plate P of the lamp 20, wires 31, 32 and 33, winding of the relay DC, wires 34: and 29, back to the secondary winding 22.

Since the relay DC is responsive to unidirectional current only it Wlll not assume its energized position even though alternating current is applied thereto. Further. since the direct current indication. relay DC depends for its energization on the flow of uni-directional current, and since such current can not flow unless the filament F of the lamp 2O tually is illuminated, it is apparent that the relay DC assumes its oleenergized position placing the relay Law as soon as the temperature of this filament falls below a predetermined value whereby the illumination of the lamp 20 may be de termined with absolute certainty. In the arrangement shown a filament F may be do energized either manually or automatically by closing the switch 36 whereupon an alternating currrent energizing circuit for the relay R is completed as follows:starting from the secondary winding 37, transformer 23, wire 38, switch or contact 36, wires 39, 32 and 40, condenser ll, wire 42, winding of the relay R, wires 43 and 2% back to the secondary winding 37. With the relay R in its energized position the back contact 27 thereof breaks the energizing circuit for the filament F so that the lamp 20 is no longer illuminated. Such de-energization of the filament F of course de-energizes the relay DC for reasons heretofore given.

lnhlock signal systems of the three or more position or multiple indication type in which either color light or position light signals are used it is desirable to give a more restrictive indication rather than no indication at it the particular lamp or lamps which are supposed to be lighted are ex tinguished.

In Fig. l of the drawings been illustrated a three condition color light signal for railways, comprising lamps G, Y and R ich are constructed to emit a green light indicating clear, a yellow light indi .ating caution or a red lightindicating danger, respectively, depending 011 the position of contact 53, automati ally positioned in accordance with trafilc conditions ahead. In the particular arrangement shown the lamps G and Y comprise Fleming valves similar to the lamp 7 illustrated in Fig. l and the lamp shown in Fig. 5, and the lamp R is one of the usual concenrated filament type heretofore used for railway signalling purposes. The filaments of the lamps, G, Y and. R- are connected to secondary windings of the transformers 50, 51 and 52, respectively. Under normal clear traihc conditions ahead as shown with the contact 58 positioned to the right, which contact may be a contact of a three-position track relay or a manually operated contact of any kind, the transformer and in turn the lamp 0 or are energized through the following circuit :loeginning at the secondary winding 5% of the transformer 55, wire 56, contact 53, wire 57, iary winding of the transformer 50, s 50 and 59, back to the secondary rind 54 .Vith the lamp illuminated a ing negative pot ntial s applied the g g of the three-element theri onic ampliher or audion 60, this by reason oi the alternating potential in secondary winding (3t rectified by the action or" the Fleming valve G and applied to the grid g? of the audion 60 through the following closed circuit 2- beginning at this secondary winding 61, wires 63 and 64, secondary winding of the transformer 62, filament F of the audion 6') to the grid (1 thereof, wires (36 and 67, from the plate P to the filament F of the lamp or Fleming valve G through wires 68 and 69 back to the secondary winding (31. By reason of the negative pulsating electromotiveforce applied to the grid 9 of the audion 60, this pulsating potential having a phase relation so as to make this pulsating potential at maximum when the voltage of the secondary winding 70 of the transformer 62 is a maximum in the direction from the plate P to the filament F of the audion G0, practically no current is caused to flow through the plate circuit of the audion 60, which plate circuit may be traced as follows :beginning at the secondary winding 70, wire 71, primary winding of the transformer 52, wire 72, plate P of the audion (30, through the ionized gas to filament F thereof, wires 64 and 73 back to the secondary winding 70. In other words, ith the lamp G energized the grid g is negatively biased so as to make the apparent internal resistance of the audion 60 very high so that practically no current can flow through the plate circuit of this audion, and consequently the red lamp R of the signal is not illuminated. If, however, the green lamp G should be de-energized for any reason, either by burning out the filament F or by reason of an open circuit in one of the energizing circuits leading to this filament, this negative bias on grid g is also no longer present, and consequently the lamp R is illuminated. The caution lamp Y is energized under caution traffic conditions by a circuit similar to that of the clear lamp G, as is obvious from the drawing. Also, only one of the lamps G and Y 'an be energized at one time, so that if the circuit for one of these lamps is completed at the contact 53 and this circuit is open at another point, neither of these lamps are energized, and no negative potential is applied to the grid so that the lamp R is illuminated.

However, if neither the lamps G or Y are energized, either because traflic conditions ahead are dangerous or beer use its filamentis burned out, the lamp R will be energized so that a more restrictive signal is automatically given in the event that one or the other of these lamps are burned out.

In the several circuit arrangements just described alternating current has been employed as a source of energy, and although alternating current preferably used because the indicating current is distinctive therefrom, it being uni-directional, it is desired to be understood that the invention is not limited to the use of alternating current and that a direct current source of energy may be used instead of the transformers shown, if desired.

In the foregoing description of various systems employing the novel indicating principle characteristic of the present invention, the combined light emitting and illumination detecting tubes, in which the detection is determined by the ionization of the gas immediately surrounding the filament have been shown conventionally. In order to more clearly illustrate how these tubes are constructed in practice, so as to permit the several functions intended to be carried out by these tubes to be utilized, one particular embodiment of a light signal unit including a light emitting tube having an additional element, conveniently called a plate. associated therewith, has been illustrated.

Referring particularly to Figs. 5 and 6 one particular type of light signal casing C has been illustrated, together with means for supporting lenses and a lamp socket therein in a manner so that the lamp socket may be adjusted with respect to such lenses, but wherein the light emitting unit including such lenses and lamp socket may be removed as a unit from such casing. The casing C has preferably a large circular opening in the front wall thereof into which may be bolted a light projecting unit including a lens barrel 80, by bolts 81. This lens barrel is provided with arecess in the large end thereof in which the outer lens 82 is adapted to be held by the bezel ring 83 suitably screw fastened to the lens barrel whereas the inner small end of this lens barrel 80 has a recess adapted to receive the inner or small lens 84, which lens is held in place by a bezel ring 85 having a downwardly projecting apron 85 as shown. In the apron 85 of the lens barrel 85 are provided slots spaced a suitable distance apart against which the shelf 86 may be bolted in various adjusted positions along a vertical line. This shelf 86 is provided with large circular openings through which the bolts 87 projecting from the lamp socket 88 may pass, these holes being so large that the socket 88 may be adjusted both sidewise with respect to the lens 84: as well as to and from such lens before these bolts are drawn down. The provision of this adjustment, together with vertical adjustment of the shelf 86 provided for, this lamp socket may be adjusted in three different planes at right angles to each other. This receptacle or lamp socket 88 is in practice so adjusted with respect to the lenses 84 and 82 that a standardized tube, such as will presently be described, when placed in said socket emits a beam of the desired spread from the doublet lense combination comprising lenses 82 and 84.

The particular two element thermionic tube illustrated comprises a lamp globe 90 having the usual bayonet type base 91 preferably having three instead of two projecting pins associated therewith, and in which llt) the filament F comprises two filament portions 92 and 93 which are connected in multiple as indicated in Fig. 6 of the drawings. Directly in back of this filament F is disposed the plate P which has an out-lead wire connected thereto leading from the base 91 of a lamp in the usual manner. In practice, this plate P is preferably constructed of carbon so as to be more susceptible to the gathering of ions emitted from the filament F, and this plate also serves a shield to pro-- vent the inner wall of the back side of the globe 90 from acting as a refiector to cause light emitted into the casing C from an outside source of light, such, for instance, as the headlight of an engine, or the like, from being reflected through the lens so as to make it appear as though the signal is illuminated, that is, from giving a false or phantom signal indication.

In practice the filaments may be treated or impregnated in any of the well known ways so as to make it more capable of electronic emission than are filaments of the usual construction.

The lens combination comprising the lenses 82 and 8a which in the railway signalling art is known as the doublet combination is of a character so that light emitted through a rather solid angle from the filament F is diverged by the small lens 84: into a conical beam striking the large lens 82, the large lens 82 being so constructed that this conical beam is in turn further concentrated into a rather narrow light beam suitable for railway signalling purposes. This particular type of lens combination is preferably employed, so that a large amount of available light emitted from the filament F may be directed along the trackway for signalling purposes by the principle of refraction and without employing reflectors.

It may be pointed out at this time that reflectors cannot be used in a light signal of this kind, because of the phantom or false signals which result if a light beam is directed into a signal casing containing a reflector through the lenses from the outside, this, for the reason, that the reflector reflects the light back out again through the lenses the inner one of which is preferably colored, thereby making it appear as though the filament were illuminated. In this type of signal even though no reflector is used difficulty has been experienced by the emission of a false or phantom signal due to light striking the inner concave surface of the lamp globe ordinarily employed in light signals of this kind, and in order to avoid such phantom signals to be displayed the plate F has been located between the ment and the back wall of the lamp globe, so that, reflection from this portion of the globe is entirely prevented.

The filament F comprising filament portions 92 and 93 connected in multiple as heretofore explained is used so as to provide a reserve filament if one of these filaments burns out. It has been found in practice, that if two filaments connected in multiple in the samelamp globe are used one of these filaments, invariably, burns out long before the other one burns out, so t iat, even though an efiective signal is still given tlr engineer or signal inspector may observe that one of the filaments have burned out and that the lamp must be replaced. The provision of two filaments in multiple, therefore, not only affords a reserve filament when one of them burns out but also afl'ords a distinctive indication giving the information that the lamp should be replaced.

If desired, the indicating relay IR may be so designed that it will assume its deenergized position if only one of the filaments 92 or 93 burns out so that this fact is immediately brought to the notice of the tower attendant when the present invention is applied to interlocking systems. In other words, a light signal has been proposed in which the illumination of the filament of an incandescent lamp may be detected by providing a plate within the globe or such lamp similar to the construction used in the well-known Fleming valve, and in which this plate is located so as to shield the back concave wall of such tube when it is placed in a light signal, whereby false indications which ordinarily may occur due to reflection of light from the inside wall of the lamp globe back through a lens so as to make it appear as though the filanent in such lamp globe is illuminated, is impossible.

Having thus shown and described a new principle whereby the fact whether or not a lamp is actually illuminated may be indicated with absolute certainty at a distant point, and having illustrated in several spe cific embodiments how this principle may be applied in practice, it is desir d to be understood that the various specific features disclosed have been shown primarily for illustrative purposes rather than for the purpose of showing the scope of the invention; also that the novel indicating principle may be applied to lamps of other types of signals, such as, semaphore signals and light signals using movable shutters, and that various modifications and additions may be made to adapt the invention to the particular problems and circumstances encountered in practice without departing from the scope of the invention or the idea of means underlying the same.

hat is desired to be secured by Letters Patent of the United States is 1. A railway signaling system, comprisin a two element lamp in the form of a 1 v rectifier of which one element comprises two filaments connected in multiple and the other a nonrefiecting conducting anode plate located back of the filament when said lamp is positioned for use, and indicating means connected in series with the gap between said plate and filament, said indicating means being so adjusted that if one of the two filaments in multiple burns out said indicating means will function to indicate the failure of such filament.

2. In a light signalling system for railways, in combination, a plurality of light signals in the forms of rectifiers depending for their functioning on the condition of their ionization, a danger signal, and means for automatically rendering said danger signal efiective only if none of said light signals is illuminated depending for its functioning on the condition of ionization of the space immediately surrounding the filaments of said light signals.

3. In a light signal of the multiple aspect t pe; in combination, three signals, each inc uding an incandescent lamp, for indicating proceed, caution, and stop respectively; the proceed and caution lamps being of the two element rectifying type and each including a, filament and an anode plate; and means depending for its operation on the ionization of the space immediately surrounding the filaments of the proceed and caution lamps for illuminating the stop lamp if both the proceed and caution lamps are extinguished.

4. In a signalling system, in combination, a plural aspect light signal, including, a single element lamp and a two element lamp in the form of a rectifier having a filament and an anode and depending for its functioning on the ionized condition of the space surrounding its filament, traffic controlled means for controlling an energizing circuit for the two element lamp, a three element vacuum tube having a plate circuit to supply energy to the single element lamp, the grid circuit of the tube including the two elements of the two element lamp and being connected to be negatively biased when the two element lamp is energized, whereby the single element lamp is energized only when the two element lamp is (le-energized.

5. In a signalling system, in combination, a plural aspect light signal, including, a single element lamp and a plurality of two element lamps in the forms of rectifiers, each having a filament and an anode and tlOiLv ing for its functioning on the ionized condi' tion of the space surrounding its filament, trafiic controlled means for controlling an energizing circuit for all of the two elemeu lamps, a three element vacuum tube having a plate circuit to supply energy to the single element lamp, the grid circuit of the tube including in multiple the two elements of the two element lamps and being connected to be negatively biased when any one of the two element lamps are energized, whereby the single element lamp is energized only when all of the two element lamps are deenergized.

6. In a signal system, in combination, two element lamps in the form of a rectifier having a filament and an anode to indicate proceed and caution respectively, traffic controlled means for controlling an energizing circuit for each of said lamps, a single element lamp for indicating stop an audion tube having a grid circuit including the two element lamps in multiple and connected to have a negative bias only when at least one of the two element lamps is energized, and an energizing circuit for the single element larlpp energized from the plate circuit of saiai tu e.

In testimony whereof I afiix my si ature.

CHARLES W. PRESCOTT. 

